[U-Boot] [PATCH] nand: fix reading after switching ecc

[Scott Wood]

On Tue, 2014-01-14 at 21:11 +0100, Jeroen Hofstee wrote:
> Hello Scott, Pekon,
> 
> On 01/13/2014 07:18 PM, Scott Wood wrote:
> >
> >>
> >>> The omap_gpmc allows switching ecc at runtime. Since
> >>> the NAND_SUBPAGE_READ flag is only set, it is kept when
> >>> switching to hw ecc, which is not correct. This leads to
> >>> calling chip->ecc.read_subpage which is not a valid
> >>> pointer. Therefore also clear the flag so reading in
> >>> hw mode works again.
> >>>
> >>> Cc: Scott Wood <scottwood at freescale.com>
> >>> Cc: Pekon Gupta <pekon at ti.com>
> >>> Cc: Nikita Kiryanov <nikita at compulab.co.il>
> >>> Signed-off-by: Jeroen Hofstee <jeroen at myspectrum.nl>
> >>> ---
> >>> drivers/mtd/nand/nand_base.c | 2 ++
> >>> 1 file changed, 2 insertions(+)
> >>>
> >>> diff --git a/drivers/mtd/nand/nand_base.c b/drivers/mtd/nand/nand_base.c
> >>> index 1ce55fd..0762a19 100644
> >>> --- a/drivers/mtd/nand/nand_base.c
> >>> +++ b/drivers/mtd/nand/nand_base.c
> >>> @@ -3354,6 +3354,8 @@ int nand_scan_tail(struct mtd_info *mtd)
> >>> 	/* Large page NAND with SOFT_ECC should support subpage reads */
> >>> 	if ((chip->ecc.mode == NAND_ECC_SOFT) && (chip->page_shift > 9))
> >>> 		chip->options |= NAND_SUBPAGE_READ;
> >>> +	else
> >>> +		chip->options &= ~NAND_SUBPAGE_READ;
> > NACK; this breaks NAND_SUBPAGE_READ with hardware ECC for drivers that
> > support it.
> 
> There is something to argue in favour of that in general, but there are
> no such drivers in u-boot at the moment though (well at least not doing 
> it on
> purpose). I don't mind moving it to gpmc, but for correctness, it 
> doesn't break
> things at the moment...

It doesn't matter if there are any such drivers at the moment.  It's a
bad change, and a gratuitous difference from Linux with which we share
this common code.

All the other cleanup required to change ECC modes is handled by the
OMAP driver; why shouldn't this be as well?

-Scott